Is There a Downside to Reverse Flow Cooling???
Thread Starter
Joined: Jan 2013
Posts: 145
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From: Largo , Florida USA
Is There a Downside to Reverse Flow Cooling??? I have the option to flow either way ... Dart Pro block, Brodix heads, water manifold, Davies Craig water pump, and an inline thermostat housing.
TECH Resident
Joined: Mar 2012
Posts: 871
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From: Texas
Reverse flow cooling was used as a band-aid for the shitty water flow characteristics of the SBC heads on the LT1s. It allowed them to run a bit more compression and timing.
My answer: Maybe? If you've got the option of easily switching from one cooling style to the other, try them both out. There's no reason why you couldn't try bumping the compression a point or two for the same octane rating, and running cooler cylinder heads.
Remember: If you run the cylinder heads/ combustion chambers too cool, you will have fuel condense on the surfaces. It's best to keep them at least 190 (F).
As far as ignition timing goes, you can try advancing that as well, but these engines don't seem to need too much in the way of advance to begin with , even with factory cooling.
Let us know what you do.
My answer: Maybe? If you've got the option of easily switching from one cooling style to the other, try them both out. There's no reason why you couldn't try bumping the compression a point or two for the same octane rating, and running cooler cylinder heads.
Remember: If you run the cylinder heads/ combustion chambers too cool, you will have fuel condense on the surfaces. It's best to keep them at least 190 (F).
As far as ignition timing goes, you can try advancing that as well, but these engines don't seem to need too much in the way of advance to begin with , even with factory cooling.
Let us know what you do.
My take on it is this….the LS platform has a very efficient chamber design and really doesn’t need…or want…cooler water temps. They wont make any more power at 180 degrees water than they will at 210 degrees water. In fact, the hotter chamber temps from a warmer coolant charge will typically make more peak torque/power than a cooler coolant charge, simply from keeping more heat on the chamber. This is not the case with the SBC. Totally the opposite in most setups with that platform.
Another thing I like about the LS coolant circuit is that with coolant entering the block first, and then upward to heads, air bubbles are carried upward naturally instead of having to fight against the flow of coolant to go upward. It clears trapped air out of the system much quicker. I personally don’t see any advantage of reversing it, but it would be interesting to see results if actual data can be derived from the experiment vs just a guess. Again…my .02
Another thing I like about the LS coolant circuit is that with coolant entering the block first, and then upward to heads, air bubbles are carried upward naturally instead of having to fight against the flow of coolant to go upward. It clears trapped air out of the system much quicker. I personally don’t see any advantage of reversing it, but it would be interesting to see results if actual data can be derived from the experiment vs just a guess. Again…my .02
It was a twenty year battle for Evans to get paid for the patent infringement. I used to buy coolant pumps for the LS from them years ago and know this story well. Regarding cooling, if you double the power you need to double the coolant flow to keep the internals from over heating. Stock style GM pump flows about 50 gallons a minute with the stock stat housing enough to cool 500 hp long duration wide open throttle. Evans pump with external stat housing flowed 110 gallons a minute or well over a thousand horsepower. Reverse flow cooling helps.
__________________
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
Last edited by Steve - Race Eng; Apr 12, 2026 at 08:53 PM. Reason: made changes
It was a twenty year battle for Evans to get paid for the patent infringement. I used to buy coolant pumps for the LS from them years ago and know this story well. Regarding cooling, if you double the power you need to double the coolant flow to keep the internals from over heating. Stock style GM pump flows about 50 gallons a minute with the stock stat housing enough to cool 500 hp long duration wide open throttle. Evans pump with external stat housing flowed 110 gallons a minute or well over a thousand horsepower. Reverse flow cooling helps.
I currently run the Edlebrock Ls pump for the Corvette. I have run the 2005-2008 OEM LS pump with the outlet hose on the passenger side then went to the 2009-2013 OEM pump with the outlet on the drivers side which is nice as it takes the hot hose away from the intake pipe. One thing I did notice is the water passages on the later LS OEM pump were much larger than the earlier version and it took a different thermostat too. The Edlebrock has larger passages and who know what they use for the impeller but it does produce more "block pressure" for better cooling. I think some places do parallel cooling which requires a different head gasket.
